1. Warm-up: Succession Read the Case Study,
“Communities Maintained by Fire”
on pages 130 – 131.
Write two things you have learned and
answer questions #1 & 2.

2. Warm-up Answers 1. New things you have learned…
The purple plant Fireweed covers the burned
forest areas of the Rocky Mountains.
Ecological Communities (Biomes) that are
maintained by fire are:
Chaparral of California, Temperate Grasslands of the Midwest, many Southern and Western Coniferous forests.
Seeds of some species will not germinate until exposed to temperatures of several hundred degrees.

3. Changes in Ecosystems: Ecological Succession

4. What is Ecological Succession?
Natural, gradual changes in the types of species that live in an area
Can be primary or secondary
The gradual replacement of one plant community by another through natural processes over time

5. Primary Succession Sides of volcanoes Landslides Flooding
Primary succession occurs where there was no previous community, such as on bare rock or sand.
Begins in a place without any soil:
Sides of volcanoes
Landslides
Flooding
Glacial retreat

6. Primary succession begins with
PIONEER SPECIES.
Pioneer organisms can tolerate extreme conditions: hot and cold; dry and wet.
Moss, dune grass, and lichens are pioneer organisms.
First, lichens that do not need soil to survive grow on rocks
Next, mosses grow to hold newly made soil

7. Pioneer Species
Low, growing moss plants trap moisture and prevent soil erosion
Lichens break down rock to form soil.

8. Lichens
Lichens are algae and fungus growing together in a mutualistic relationship.
Algae make the food
Fungus anchor and capture water.

9. Primary Succession
Soil starts to form as lichens and the forces of weather and erosion help break down rocks into smaller pieces
When lichens die, they decompose, adding small amounts of organic matter to the rock to make soil

10. Primary Succession with lichens and mosses.

11. Primary Succession
Simple plants like mosses and ferns can grow in the new soil

12. Primary Succession
The simple plants die, adding more organic material (nutrients to the soil)
The soil layer thickens, and grasses, wildflowers, and other plants begin to take over

13. Primary Succession
These plants die, and they add more nutrients to the soil.
Shrubs and trees can survive now.

14. Primary Succession
Insects, small birds, and mammals have begun to move into the area.
What was once bare rock, now supports a variety of life.

17. Secondary Succession
Begins in a place that already has soil and was once the home of living organisms
Occurs faster and has different pioneer species than primary succession

18. Secondary Succession
Newer communities make it harder for the older communities to survive.
Example: Younger birch trees will have a harder time competing with taller, older birch trees for sun, but a shade loving tree may replace the smaller birch trees.

19. When does secondary succession occur?
After forest fires
After cultivated land is abandoned
Temporary flooding from storms, etc.

21. Climax Community
A relatively stable group of plants and animals that is the end result of the succession process
However, stability never happens for long in ecology! The only constant is CHANGE!
Does not always mean big trees
Grasses in prairies
Cacti in deserts

22. The following slide is an example of the Secondary Succession of a deep freshwater pond.